Oligomeric, ethylenically unsaturated molecules made from the polymerization of alpha-olefins are known. For example, U.S. Pat. No. 8,748,361 B2 discloses a mixture comprising unsaturated polyalpha-olefin (“uPAO”) material made from, e.g., oligomerization of alpha-olefins in the presence of metallocene catalysts. It was disclosed in this reference that the uPAOs could comprise, among others, vinyls, vinylenes, 1,2-di-substituted vinylenes, and tri-substituted vinylenes. The vinyls and vinylidenes are terminal olefins, while the di- and tri-substituted vinylene olefins are internal olefins.
In U.S. Pat. No. 8,748,361 B2, mixtures of the uPAOs produced from the polymerization step were subsequently hydrogenated by hydrogen using a hydrogenation catalyst. A great majority of the C═C double bonds in the mixture were then hydrogenated to form a substantially saturated, stable, aliphatic PAO mixture which, in turn, can be separated by distillation to obtain a hydrogenated PAO material that is particularly suitable as the base stock for lubricating oil compositions used in various applications. To the extent the presence of C═C bonds in the PAO molecules in a lubricating oil composition is considered generally detrimental to the performance of the oil, especially to the oxidation stability thereof, it is highly desired that the uPAO has an overall composition that would result in saturation of the C═C bonds at a degree as high as possible in the hydrogenation step.
Recently, however, research and development in various chemical fields reveal that the ethylenically unsaturated PAO materials prepared from oligomerization of linear alpha-olefins can be particularly advantageously used as an intermediate for making various specialty chemicals because of the reactivity of the C═C double bond present in molecular structure of the oligomer molecules. For example, various chemical functional groups can be bonded to the carbon backbone of the unsaturated PAO molecule when a chemical agent reactive with the C═C bond is allowed to contact the unsaturated PAO material. The functional group thus introduced onto the PAO structure can bring about unique properties to the functionalized and saturated PAO molecules.
It has been found that the reactivity of the C═C bonds in vinyls, vinylidenes, 1,2-di-substituted vinylenes and tri-substituted vinylenes are different with regard to many chemical functionalization agents. For a specific type of functionalization agent, one or more particular type(s) of olefin(s) may be more desirable than the other(s). In addition, uPAOs having various molecular weight and molecular weight distribution and differing reactivities may be desired for making differing derivatives comprising differing functional groups thereon. Vinylidenes and tri-substituted vinylenes are more reactive than 1,2-di-substituted vinylenes with many common reagents reactive with C═C double bonds.
U.S. Publication No. 2013/0023633 A1 discloses metallocene compounds and use thereof in making polyolefins rich in vinyls.
There remains a need for unsaturated PAO materials particularly useful as intermediate materials for making functionalized PAOs.